The case for using a blockchain boils down to a concept in computer security known as “information integrity.”

This September, DARPA, which stands for Defense Advanced Research Projects Agency (the agency helped create the internet, among other things), awarded a $1.8 million contract to a computer security firm called Galois. The firm’s assignment is to formally verify—a sort of computer-code audit, using mathematics—a particular type of blockchain tech supplied by a company called Guardtime. Formal verification is one way to build nearly unhackable code, and it’s a big part of DARPA’s approach to security.

If the verification goes well, it would inch DARPA closer to using some form of blockchain technology for the military.

The prospect of the US military using a blockchain to secure critical data could spark a boom in uses of the technology outside finance. Investors poured $134 million into blockchain startups in the first quarter of 2016, according to research by trade publication CoinDesk. These firms have focused overwhelmingly on financial applications to date. But information security represents a huge new market for blockchain tech vendors, accounting for $75 billion in spending last year, and projected to hit $108 billion in 2019

Each party in the network has its own copy of the blockchain attached to every asset. As long as the chains are in sync, all parties can be confident that the asset or transaction is valid.

Blockchain adds a persistent code and security layer to the process. The code — or block — is unique to that asset and stays with it forever. Blocks are time-stamped and protected with encryption that is considered unbreakable. The blockchain record on each computer in the network is called a ledger.

Each time the asset is modified, a new block is added, creating a chain (hence the term). All parties in the network receive a copy of the updated asset with the new blockchain. As long as the blockchains match, there can be no question about authenticity; if any blockchain doesn’t match the others, the asset is considered invalid and the update is rejected. Updates happen very quickly, usually in milliseconds.

When a Bitcoin transaction occurs, the previous transaction’s hash and the public key of the next owner are digitally signed with the current owner’s private encryption key. If you want to transfer your Bitcoin (that is, buy something), you have to have your secret key. No key, no possession.

Once an entry is written into the block chain, it cannot be altered without regenerating the previous blocks. (In other words, data can be added to the transactions database, but it cannot be removed.)